In recent years, there have been proposed and developed various automatic lane deviation prevention control technologies and vehicle dynamics control technologies. On automotive vehicles having both the vehicle dynamics control (VDC) function and lane deviation prevention (LDP) function, generally, there are two types of lane deviation prevention control, namely, an LDP control system using a steering actuator and an LDP control system using braking force actuators. In the steering-actuator equipped LDP control system, lane deviation is prevented by producing a yaw moment by way of steering-torque control whose controlled variable is determined depending on a host vehicle's lateral displacement or a host vehicle's lateral deviation from a central axis (a reference axis) of the current host vehicle's driving lane. One such steering-actuator equipped LDP control system has been disclosed in Japanese Patent Provisional Publication No. 11-180327 (hereinafter is referred to as JP11-180327).
On the other hand, in the braking-force-actuator equipped LDP control system, lane deviation is prevented by producing a yaw moment by controlling braking force actuators, such as an ABS-system hydraulic modulator, depending on a host vehicle's lateral deviation from a central axis of the current host vehicle's driving lane. Usually, in order to produce the yaw moment for lane deviation avoidance, braking forces are applied to the road wheels opposite to the direction that the lane deviation occurs. One such braking-force-actuator equipped LDP control system has been disclosed in Japanese Patent Provisional Publication Nos. 2000-33860 (hereinafter is referred to as JP2000-33860) and 2001-310719 (hereinafter is referred to as JP2001-310719).
LDP control systems as disclosed in JP11-180327, JP2000-33860, and JP2001-310719, often use a vehicle-mounted charge-coupled device (CCD) camera and a camera controller as an external recognizing sensor, which functions to detect a position of the host vehicle within the host vehicle's traffic lane and whose sensor signal is used for the lane deviation avoidance control or lane deviation prevention control. Within the camera controller, on the basis of an image-processing picture image data in front of the host vehicle and captured by the CCD camera, a white lane marking, such as a white line, is detected and thus the current host vehicle's traffic lane, exactly, the current position information of the host vehicle within the driving lane, in other words, information regarding whether the host vehicle tends to deviate from the driving lane, is detected.